Aqueous solutions of acid gases and ammonia also having fixed and free ammonia salts can be obtained from the washing of coal carbonization gases, e.g., the by-products from coke ovens. The separation of the ammonia and acid gases is practiced by using distillation apparatus with a free and a fixed ammonia section, see "Industrial Chemistry", E. R. Riegel, Reinhold Publishing Corporation, N.Y., 1942, pp 265-268. This system, however, has had problems in reaching consistent low levels of ammonia and acid gases in the effluent aqueous solution, in efficiency of separation of both acid gases and ammonia, energy consumption per gallon of aqueous solution treated, deposits or solids or fouling in the apparatus, stable operation, and in large quantities of sludge formed when lime is used to free the fixed ammonia.